Spiral wound paper tube having seamless outer surface



Oct. 3, 1961 c. K. DUNLAP 3,002,433

SPIRAL WOUND PAPER TUBE HAVING SEAMLESS OUTER SURFACE Filed Jan. lO, 1958 2 SheetS-Shee'h 1 Fiyi .ze Z0 20 zo f5(\ s A figg? INI/EN TOR.

CHARLES K. PUNLAP TTORNEKS C. K. DUNLAP Oct. 3, 1961 SPIRAL WOUND PAPER TUBE HAVING SEAMLESS OUTER SURFACE Filed Jan. lO. 1958 2 Sheets-Sheet 2 IN VEN TOR. CHA RLES A. DUNLAP BY wrm- @4M ATTQRNEV@ iin cited States Fatemi F 3,062,433 SPIRAL WGUND PAPER TUBE HAVEN@ SEAMLESS UTER SURFACE Charies ii. Dunlap, Hartsviile, SLC., assigner to Sunoco Products Company, a corporation of South Carolina Filed dan. 10, 1955i, Ser. No. 768,273 ll Claim. (Cl. 93--94) This invention relates in general to the spiral winding of paper tubes and more particularly to Ia spiral wound tubular paper body in which the outer surface seam is made substantially indiscernible, so as to provide an outer surface that is seamless for all practical purposes, and to the method by which this result is obtained.

Spirai wound paper tubes are employed to a large extent as winding corm for various sorts of sheet material, and are well adapted for this purpose because they have an inherent relatively high strength and because spiral winding is a particularly eii'cient and relatively inexpensive manufacturing operation. However, because the usual edge abutting disposition of the plies in a spiral wound paper tube characteristically results -in Ia spiral depression or irregularity at the tube surfaces, substantial diioulty has been encountered in adapting spiral tube winding cores satisfactorily for use with iiexible sheet materials, such as cellophane, for example, in which any imperfection inthe winding core will be reilected through each of the windings placed on the core to introduce a repeating imperfection in the sheet material that can render it useless.

Lceordirry to the present invention this diiiiculty is overcome so as to provide a spiral wound tubular body I having an entirely smooth and seamless outer surface by spiral win-ding lall ofthe paper tube plies, except the Iouter one, in edge abutting relation while spiral winding the outer ply therewith to overlap itself fully at a beveled edge portion formed `along at least one edge thereof, and then grinding and ybutiing the entire exterior surface of the outer ply smooth. In this manner it becomes possible to wind the outer ply so as to provide a tight and secure seam without requiring any particular attention to the surface smoothness at the seam during winding, and then to impart a huish over the entire outer ply surface of such smoothness that the identity of the spiral seam therein is substantially lost. In `a typical spiral tube winding core formed in yaccordance with the present invention, the outer ply spiral seam remains only faintly visible and cannot be detected at all by touch, the finishing treatment having in practical effect produced a continuous surface across the spiral seam joint.

The foregoing and other features of the present invention are described in further detail below in connection with the accompanying drawings, in which:

FlG. l is a schematic representation of the manner in which a spiral wound tubular body is formed according to the present invention;

FIG. 2 is an exaggerated schematic representation in longitudinal section of the manner in which the outer ply is wotmd as illustrated in FIG. l;

FlG. 3 is =a further schematic illustration corresponding to FIG. 2 but representing the use of an alternative form of outer ply;

FIG. 4 is an additional schematic illustration corre-x sponding to FIGS. 2 and 3 and representing the use of a still further alternative form of outer ply;

FiG. 5 is an exaggerated longitudinal section of a typical wall istructure fora spiral wound tubular body formed in accordance with the present invention with lany of the alternative forms of outer ply illustrated in FIGS. 2, 3 and 4;

FIG. 6 is a fragmentary exterior face plan view of an outer ply such as is illustrated in FIGS. l and 2;

Patented Oct. 3, 1961 FIG. 7 is a fragmentary elevation illustrating the api pearance of ya spiral wound tubular body immediately after winding when formed in accordance with the present invention with an outer ply of the form illustrated in FIG. 6;

FIG. 8 is a corresponding fragmentary elevation illust-rating the appearance of the FIG. 7 spiral wound tubular body after grinding;

FiG. 9 is a corresponding fragmentary elevation illustrcting :the appearance of the FIG. 8 spiral Wound tubular body after treating in preparation for builing; and

FIG. l0 is la corresponding fragmentary elevation illustrating the appearance of the FlG. 9 spiral wound tubular body after buiiing to complete a winding core in accordance with the present invention.

referriug now -in particular to the drawings, FIG. l 'lus-,trates the spiral winding of an outer paper ply 1G with a plurality of inner plies l2, 14 and 16 to form a spiral wound tube structure T, the outer ply 10 having outwardly facing beveled edge portions 18 and 2) formed along both edges thereof as is described more in detail further below. FIG. l further illustrates the manner in which the tube structure T is processed to form a seamless surface thereon in accordance with the present invention.

The spiral winding of the paper plies 1t), l2, 14 and 16 may be carried out in the usual manner on a mandrel 50 by means of a conventionally arranged winding belt 52, the outer ply l@ and intermediate plies l2 and 14 having firs-t had adhesive applied to the under surfaces thereof for securing the resulting spiral wound tube structure T. Upon emergence from the winding belt 52, suitable means such as is inmcated at 5d in FIG. 1 is arranged to heat the wound tube structure T so as to set the securing or laminating adhesive therein and otherwise dry the tube structure before further processing. The further processing then comprises grinding the entire outer surface of the tube structure T by means of one o-r more abrasive belts Se or the like as indicated at 56, treating the ground tube structure i with a surface nishing material applied suitably from a spr-ay line 58 supplied from a reservoir 60,

and finally buling or polishing the ground and treated tube structure T by means of a leather builing belt 62 or the like to complete the seamless outer surface of the present invention.

The manner in which the outer ply 'l0 behaves during the winding operation is illustrated further in FIG. 2 in which a sectional outline of the outer ply l0, supplied for winding with outwardly facing beveled edge portions in and 2d at both edges thereof, is represented together with a comparable sectional outline representing a series of the outer ply spiral convolutions after winding. As indicated in FIG. 2 the outer ply 10 is wound so as to overlap fully the beveled edge portion 18 at the trailing edge of each preceding spiral convolution, the leading beveled edge portion 2d of the outer ply 10 as supplied for winding being deformed or displaced outwardly during the winding operation, as indicated in FIG. 2, to form a secure and tight spiral seam joint at the beveled edge portion 1S it overlaps.

As the beveled edge portions 18 and 20 may usually be formed most conveniently and to the best advantage on the outer ply iti by abrasive grinding of the outer ply edge portions prior to winding, the result of winding the outer ply lil in the above described manner is to turn the ground face of the leading beveled edge portion 20 outwardly at the surface of the resulting spiral wound tube structure T, as noted in further detail below, although it should be mentioned here that the apparent irregularity thus introduced at the tube surface is of no consequence according to the present invention, the emphasis at this stage being devoted to formation of the best possible spiral seam joint and the arrangement of the beveled edge anca/gap portions t8 and 2t) to face outwardly allowing adhesive to be applied readily over the entire inner face of the outer ply lit) and thereby be available without special attention as fully at the spiral seam asV elsewhere.

` However, the results obtained according to the present invention are not dependent upon use of an outer ply lil of the particular form illustrated in FIGS. l and 2. lf desired, an outer ply lll may be employed as illustrated in FIG. 3 with an outwardly facing beveled edge portion '18( ground only at the trailing edge thereof and with the leading edge 20' being left plain so as to be thrown up in a spiral ridge formation upon winding to overlap the tifailing beveled edge portion f8. In this case, too, the inner surface of the outer ply lll' is originally left undisturbed for application of adhesive thereto in the usual manner prior to the winding operation, while the single beveled edge portion 18' thereon requires less grinding prior to the winding operation. ln general, the choice of this alternative form of outer ply l as compared with the previously described form of outer ply lll will depend upon whether the type of paper being used and the processing equipment available and other` such factors allows the leading edge of the ply to be ground most etliciently before or after winding.

FIG. 4 illustrates a further alternative form of outer ply lll" in which a trailing beveled edge portion 18" isk ground to face outwardly while a leading beveled edge portion Ztl" is ground in staggered relation to face inwardly, so that the winding operation can be carried out without requiring any deformation of the outer ply itl" at its leading edge. An outer ply lil" of this form may be used to advantage when thev paper being employed is of a plated type in which a special outer surface formation has been provided that should not be displaced along the spiral seam joint.

In any event, the resulting spiral wound tube structure T formed according to the present invention has the structural arrangement illustrated in FIG. 5 in which the inner plies 12, 14 and 16 are shown wound in the usual edge abutting arrangement, thatcharacteristically results in gaps between the adjacent ply edges, while the outer plyy is provided with a beveled spiral seam joint that may be wound tight and secure according to the present invention. Except for this tight spiral seam joint in the outer ply, the spiral wound tubestructure T is of conventional form and may employ plies of the usual thickness or weight normally employed in forming spiral tubes of' this sort. A common weight range for the plies of such spiral tube constructions is from about 2O to 37 point and the outer ply lll arranged according to the present invention may beselected within this weight range on the basis of usual considerations as if a conventional spiral tube construction were to be wound.

FIG. 6 of the drawings illustrates more. realistically the appearance of an outer ply l0 provided according to the present invention with the beveled edge portions l and 2@ ground along the opposite edges thereof, the grinding of which normally results in rendering the ply edges irregular somewhat in the nature of a deckled edge, and in this connection it may be noted that a paper machine deckle might be employed to provide the necessary beveled edge portion if the ply widths desired could be obtained feasibly from a paper machine sheet. The remaining surface texture and condition of the outer ply is not of particular importance as long as it is adapted adequately for effective spiral winding.

FIG. 7 illustrates the appearance of a fragmentary section of spiral wound tube structure Tw as it appears irnmediately after winding when an outer ply 1li of the form illustrated in FIG. 6 is employed, the ground face of the leading beveled edge portion appearing at the outer surface of the tube section Tw adjacent to the spiral seam s, and having a somewhat irregular form as a result of the irregular edges of the outer ply 10 that are caused by grinding the beveled edge portions 18 and 20 thereon.

Upon setting of the adhesive in the wound tube structure Tw by heating at 54, as previously mentioned, and subsequent grinding of the entire tube surface at 56, the surface appearance changes substantially as illustrated in lTG. 8 which shows a ground tube section Tg on which t d outer surface presents a substantially uniform t and the spiral seam s is not nearly so readily distinguished. At stage, the entire surface of the tube section Tg presents a niass of slightly protruding fibers and thc result of this condition is to bridge substantially the spiral seam s in preperation for eliminating its physical effect at the tube surface.

FIG. 9 next illustrates the appearance of a tube section Tt after it has been treated, the result of thistreatment being to lay the previously protruding ground fibers and consequently to make the spiral seam somewhat more visible. Also, depending upon the type of treating composition employed a more or less pronounced color changeV is apt to appear at the tube surface. This particular surface finishing material used may be selected in a matter of wide choice, although in the usual case exceptionally good results areV obtained with an ethyl cellulose solution, to which wax may be added if a waterproofing effect is desired.

' Finally, FIG. l() illustrates the appearance of a tube section Tb after bufting to produce the seamless outer surface. of the present invention. At this stage a slickv smooth surface is developed on the tube structure and the spiral seam s again fades very substantially so that it is hardly visible any longer; and cannotbe elt at the tube surface.

The grinding, treating and buing steps employed in. producing the seamless spiral tube. surface of,l theV present invention substantially complement eachY other iny that the grinding step, in addition to initially placing a smooth continuous surface on the tube strupture, prepares the tube surface advantageously to receive a surface finishing material etectively at the treating stepJ while the treating step can bev carriedoutwithout impairing the continuous smoothness obtained by grinding and at the Sam@ time conditioning the tube s ur ceso that the final builing step can be carriedroutprimwily for polishing effect without requiring anyvsrubstantial sizing action onV the tube structure which has. already been wund Smooth- Tli, present inventief has. been described in detail @have far Purposes Qi; illustrati@ only arid iS not iiitended to bel limited by this description or otherwise except as defined in the appended claim.

I claim:

A. mathOdLQf, Producing a, Spiraily Wound tube, having a Substantially indisponible Qutr surfa Sgam` camnrisiitg the steps of, beveling at least one edge of the outer surf ace of a paper strip to be wound and to constitute the outer surface of the tube to f ovrm an outwardly facing bevel, spirally winding said paper strip in overlapping relationship to form a spirally wound tube, winding said outer strip with its beveled edge overlapped by the edge of the adjacent convolution to thereby deflect said adjacent convolution edge, radially outward producing a surface irregularity throughout the extent of the spiral seam, grinding the entire 'exterior surface of said tube only sufficient to remove the surface irregularity resulting from said dellection and to produce a uniform exterior surface on said tube having a substantially indisceruible Quiet Surface- Spiial. Seam- Referenees Cited in the tile of tnsv patent UNITED STATES PATENTS 1,287,945 Ford -..X A ,.V Dec. 17, 1918 2,751,936V Dunlap et al. n n June 26, 1956 2,785,700 Yovanovich Mar. 19, 1957 2,895,511 Soltrnan V V July 21, 1959 

